package homework;

import java.util.Scanner;

public class Test4 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int score = sc.nextInt();
        if (score>=0&&score<=100){
            if (score>=90){
                System.out.println("A");
            }else if (score>=60){
                System.out.println("B");
            }else{
                System.out.println("C");
            }
        }else {
            System.out.println("数据错误");
        }
    }
}
